The aim of this work was to evaluate nutritional status, body composition, and proportion in relation to socioenvironmental conditions of residence in the infant-juvenile population of three towns in the district of Punta Indio, in Buenos Aires. A cross-sectional study was performed in 845 children (47.5% male and 52.5% female) 3 to 15 years old. Weight, height, sitting height, arm circumference, and triceps and subscapular skinfolds were surveyed, and nutritional indicators, body composition, and proportion were calculated using the Third National Health and Nutrition Examination Survey reference. Socio-environmental information was obtained through structured questionnaires and was processed with a Categorical Principal Components Analysis which allowed to distinguish four groups: I) “favored urban”; II) “intermediate urban”; III) “urban unfavorable”, and IV) “rural”. In each group, prevalence of nutritional status was also calculated and compared using Fisher’s exact test. The results for the total population indicated 3.8% of undernutrition, 13.1% of overweight, and 10.9% of obesity. All types of malnutrition were accompanied by changes in body composition. Group IV was different from the other groups in that it did not present cases of chronic undernutrition. These results allow us to conclude that the studied population has experienced an advanced nutrition transition, characterized by low prevalence of undernutrition and high prevalence of overweight and obesity. This situation can be related to profound economic changes that have recently occurred in the district of Punta Indio, which have not led to the elimination of malnutrition but to changing its polarity towards excess weight.